libmodbus_client.cpp

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/*
 * Copyright (c) 2018 Pilz GmbH & Co. KG
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <ros/ros.h>
 
#include <cstddef>
#include <vector>
#include <errno.h>
#include <limits>
#include <thread>
#include <prbt_hardware_support/libmodbus_client.h>
#include <prbt_hardware_support/modbus_check_ip_connection.h>
#include <prbt_hardware_support/pilz_modbus_exceptions.h>
 
namespace prbt_hardware_support
{
LibModbusClient::~LibModbusClient()
{
  close();
}
 
bool LibModbusClient::init(const char* ip, unsigned int port)
{
  // The following check results from Ubuntu 18.04 using libmodbus 3.0.6 where a timeout cannot be set on
  // modbus_connect.
  // As a result trying to connect with to a wrong address could modbus_connect could get stuck for up to over 100
  // seconds. The precheck lowers this risk by performing a quick connect to the given address.
  //
  // If you read this comment at a time where Ubuntu 18.04 is no longer relevant please remove this check and define a
  // timeout for modbus_connect(). Thank you!
  if (!checkIPConnection(ip, port))
  {
    ROS_ERROR_STREAM("Precheck for connection to " << ip << ":" << port << " failed. " << modbus_strerror(errno)
                                                   << ".");
    return false;
  }
 
  modbus_connection_ = modbus_new_tcp(ip, static_cast<int>(port));
 
  if (modbus_connect(modbus_connection_) == -1)
  {
    // LCOV_EXCL_START the following lines are hard to cover since the above checkIPConnection should prevent
    // exactly this situation
    ROS_ERROR_STREAM_NAMED("LibModbusClient",
                           "Could not establish modbus connection. " << modbus_strerror(errno) << ".");
    modbus_free(modbus_connection_);
    modbus_connection_ = nullptr;
    return false;
    // LCOV_EXCL_STOP
  }
 
  return true;
}
 
void LibModbusClient::setResponseTimeoutInMs(unsigned long timeout_ms)
{
  uint32_t tv_sec = static_cast<uint32_t>(timeout_ms / 1000);
  uint32_t tv_usec = static_cast<uint32_t>((timeout_ms % 1000) * 1000);
  modbus_set_response_timeout(modbus_connection_, tv_sec, tv_usec);
}
 
unsigned long LibModbusClient::getResponseTimeoutInMs()
{
  uint32_t tv_sec;
  uint32_t tv_usec;
  modbus_get_response_timeout(modbus_connection_, &tv_sec, &tv_usec);
  return static_cast<unsigned long>(tv_sec * 1000L + (tv_usec / 1000L));
}
 
RegCont LibModbusClient::readHoldingRegister(int addr, int nb)
{
  ROS_DEBUG("readHoldingRegister()");
  if (modbus_connection_ == nullptr)
  {
    throw ModbusExceptionDisconnect("Modbus disconnected!");
  }
 
  RegCont tab_reg(static_cast<RegCont::size_type>(nb));
  int rc{ -1 };
 
  rc = modbus_read_registers(modbus_connection_, addr, nb, tab_reg.data());
  if (rc == -1)
  {
    std::ostringstream err_stream;
    err_stream << "Failed to read " << nb;
    err_stream << " registers starting from " << addr;
    err_stream << " with err: " << modbus_strerror(errno);
    ROS_ERROR_STREAM_NAMED("LibModbusClient", err_stream.str());
    throw ModbusExceptionDisconnect(err_stream.str());
  }
 
  return tab_reg;
}
 
RegCont LibModbusClient::writeReadHoldingRegister(const int write_addr, const RegCont& write_reg, const int read_addr,
                                                  const int read_nb)
{
  if (modbus_connection_ == nullptr)
  {
    throw ModbusExceptionDisconnect("Modbus disconnected!");
  }
 
  if (read_nb < 0)
  {
    throw std::invalid_argument("Argument \"read_nb\" must not be negative");
  }
  RegCont read_reg(static_cast<RegCont::size_type>(read_nb));
 
  if (write_reg.size() > static_cast<unsigned int>(std::numeric_limits<int>::max()))
  {
    throw std::invalid_argument("Argument \"write_reg\" must not exceed max value of type \"int\"");
  }
 
  int rc{ -1 };
  rc = modbus_write_and_read_registers(modbus_connection_, write_addr, static_cast<int>(write_reg.size()),
                                       write_reg.data(), read_addr, read_nb, read_reg.data());
  ROS_DEBUG_NAMED("LibModbusClient", "modbus_write_and_read_registers: writing from %i %i registers\
                                      and reading from %i %i registers",
                  write_addr, static_cast<int>(write_reg.size()), read_addr, read_nb);
  if (rc == -1)
  {
    std::string err = "Failed to write and read modbus registers: ";
    err.append(modbus_strerror(errno));
    ROS_ERROR_STREAM_NAMED("LibModbusClient", err);
    throw ModbusExceptionDisconnect(err);
  }
 
  return read_reg;
}
 
void LibModbusClient::close()
{
  if (modbus_connection_)
  {
    modbus_close(modbus_connection_);
    modbus_free(modbus_connection_);
    modbus_connection_ = nullptr;
  }
}
 
}  // namespace prbt_hardware_support